Trump's actions drew criticism from many quarters, including the British government at 10 Downing Street, which said Trump was "wrong" to promote the group's "hateful narratives".
The White House scrambled to limit the fallout, saying even if the anti-Muslim videos were misleading, Trump was pointing out a real problem.
"The threat is real, and that's what the president is talking about," said Trump's spokeswoman Sarah Sanders.
One of the videos claims to show a Muslim beating up a Dutch boy on crutches. Another is described as showing an Islamist mob pushing a teenager off a rooftop. The veracity of both is in doubt.
The third allegedly depicts a Muslim throwing down and smashing a statue of the Virgin Mary.
'Spreading hatred has consequences'
The footage was originally posted by Jayda Fransen, deputy leader of the far-right group Britain First, which hailed Trump for his support.
“The president of the United States, Donald Trump, has retweeted three of deputy leader Jayda Fransen’s Twitter videos!” the group tweeted in triumph.
“Donald Trump himself has retweeted these videos and has around 44 million followers! God bless you Trump! God bless America!”
Fransen was found guilty last year of a hate crime after hurling abuse at a Muslim woman wearing a hijab.
This screenshot from President Donald Trump's Twitter account shows three retweets that he posted early Wednesday morning, Nov. 29, 2017 (AAP) Source: AAP
Britain First, which was formed in 2011 and is known for picketing outside mosques, has run and lost in several British and European parliament elections.
Brendan Cox, widower of MP Jo Cox who was murdered by a right-wing extremist last year, said: "Trump has legitimized the far right in his own country, now he's trying to do it in ours.
"Spreading hatred has consequences and the president should be ashamed of himself," he said.
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'Abhorrent, dangerous'
David Lammy, an MP for the opposition Labour Party, said: "The president of the United States is promoting a fascist, racist, extremist hate group whose leaders have been arrested and convicted.
"He is no ally or friend of ours," he said.
Stephen Doughty, another Labour MP, called the videos "highly inflammatory" and his colleague Yvette Cooper said Trump had given Fransen a "huge platform".
Opposition leader Jeremy Corbyn said the retweets were "abhorrent, dangerous and a threat."
Fransen and Britain First leader Paul Golding were due to appear in court on Wednesday for a pre-trial review on charges of "threatening, abusive or insulting words or behavior" over a speech she made in Belfast.
Trump's interventions in British politics and controversial foreign policy have strained the so-called "special relationship".
He has infuriated British authorities with his tweets on terrorism in Britain, including highly publicized run-ins with London's Muslim mayor Sadiq Khan.
Wednesday's retweets were part of an early morning burst in which Trump again dismissed CNN as "Fake News" and insisted the US economy was in "record territory" by many measures.
Trump also said consumer confidence was at an all-time high.
"I guess somebody likes me (my policies)!" the president wrote.
